As smart phones or tablet personal computers (PCs) are widely distributed in recent years, technology for contact position measurement devices embedded therein are rapidly developing. The smart phones or tablet PCs are mainly provided with touch screens, and users may input touch commands through the touch screens.
In particular, when a user's touch command is inputted through a capacitance method, a change in the capacitance formed between a contact object and a touch screen may be sensed, or a change in the capacitance between an X-axis electrode and a Y-axis electrode included in a touch panel of a touch screen may be sensed.
A capacitance value sensed in each method is in inverse proportion to a distance between the contact object and the touch screen. That is, when the distance between the contact object and the touch screen is longer than or equal to a predetermined threshold distance, the capacitance value sensed through the touch screen is very small.
When such a small capacitance value is sensed as described above, a signal to noise ratio (SNR) regarding a noise caused by each electrode or an ambient environment is reduced and thus there is a problem that an exact position of the contact object cannot be sensed.